This invention relates in general to electrostatography, in particular to substrates for electrophotoconductive imaging members having multiple layers.
Flexible electrostatographic belt imaging members are well known in the art. Typical electrostatographic flexible belt imaging members include, for example, photoreceptors for electrophotographic imaging systems and electroreceptors or ionographic imaging members for electrographic imaging systems. In electrophotography, an electrophotographic plate containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging its surface. The plate is then exposed to a pattern of activating electromagnetic radiation such as light. The radiation selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer. The resulting visible image may then be transferred from the electrophotographic plate to a support such as a paper. This imaging process may be repeated many times with reusable photoconductive insulating layers.
An electrophotographic imaging member may be provided in a number of forms. For example, the imaging member may be a homogeneous layer of a single material such as vitreous selenium or it may be a composite layer containing a photoconductor and another material. One type of composite imaging member comprises a layer of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. U.S. Pat. No. 4,265,990 discloses a layered photoreceptor having separate photogenerating and charge transport layers. The photogenerating layer is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer.
U.S. Pat. No. 4,026,703 to Hayashi et al discloses a photoreceptor comprising a substrate. Included in a list of plastic films which may preferably be used is polyimide (col. 6, lines 7-20).
U.S. Pat. No. 4,971,873 to Pavlisko et al discloses photoconductor elements containing a solvent soluble polyimide binder in a barrier layer, a charge generating layer of a single-layer photoconductive element or a charge generating layer and/or a charge transport layer.
U.S. Pat. No. 4,747,992 to Sypula et al discloses a process for fabricating a belt. The belt may be used for electrostatographic imaging members as a substrate layer. The substrate layer may comprise any of a number of film forming polymers, including polycarbonates, polysulfones, polyesters, and polyvinylfluoride. Electrostatographic imaging members are also disclosed which include photogenerating layers containing photoconductive compositions and/or pigments and a resinous binder. The basis for selection from among the materials for the charge generating layer and the substrate is not disclosed.
U.S. Pat. No. 4,756,993 to Kitatani et al discloses an electrophotographic photoreceptor comprising a light-transmitting conductive support comprised of a transparent thermoplastic resin film. The resins to be used for the conductive support include polyesters, polycarbonates, polyamides, acrylic resins, polyamide- imide resins, polystyrene, polyacetals, polyolefins, etc. An electrophotographic photosensitive layer is disclosed as being an organic photoconductive layer composed of an organic photoconductive substance. Polyvinylcarbazole and its derivatives are disclosed as one such organic photoconductive substance.
U.S. Pat. No. 4,895,784 to Shirai discloses a photoconductive member comprising a drum-shaped substrate and a photoconductive layer. The substrate may be either electroconductive or dielectric. Dielectric supports include films or sheets of synthetic resins, including polyester, polyethylene, polycarbonates, cellulose acetates, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, etc. The photoconductive layer may be a vacuum deposited layer comprising an amorphous material comprising silicon atoms.
U.S. Pat. No. 4,582,772 to Teuscher et al discloses layered photoconductive imaging devices comprising an endless flexible belt substrate of an insulating material which can be selected from polycarbonates, polyurethanes, polyesters and polyamides. The thickness of the substrate is in the range of from about 50 microns to about 150 microns.
U.S. Pat. No. 4,702,980 to Matsuura et al discloses an electrostatic recording medium. The recording medium is a sheet-like product prepared from polyolefins.
As more advanced, higher speed electrophotographic copiers, duplicators and printers were developed, degradation of image quality was encountered during extended cycling. Moreover, complex, highly sophisticated duplicating and printing systems operating at very high speeds have placed stringent requirements including narrow operating limits on photoreceptors.
Modern composite imaging members have been developed which have numerous layers which are highly flexible and exhibit predictable electrical characteristics within narrow operating limits to provide excellent images over many thousands of cycles. One type of multilayered photoreceptor that has been employed as a belt in electrophotographic imaging systems comprises a substrate, a conductive layer, a blocking layer, an adhesive layer, a charge generating layer, and a charge transport layer. This photoreceptor may also comprise additional layers such as an anti-curl layer and an optional overcoating layer.
Since electrophotography is a photoelectric process, a great deal of attention has been focused on electrical performance of layers. There is an ongoing need to improve the performance of photoreceptors.